This invention relates to solar air heating, and more particularly, to a method and apparatus for heating gases which selectively uses heat from the winter sun and rejects heat from the summer sun.
Solar air heaters have been known for many years. They usually have a transparent cover, a radiation absorbing surface and an insulating backing. Air is passed across the radiation absorbing surface which is heated by the sun. Typical of these solar air heaters are those described in an article entitled "Black-Painted Solar Air Heaters of Conventional Design" by Austin Whillier published on pages 31-37 of Solar Energy Vol. 8, No. 1, 1964.
Many efforts have been made to improve the efficiency of such heaters by providing selective black coatings on the radiation absorbing surface to reduce reradiation losses and by decreasing the heat losses through the transparent cover by the use of multiple glass covers. While many of these efforts have proven quite useful and, in fact, highly successful, the utilization of multiple covers simply tends to increase the cost of such heaters prohibitively. Further, the utilization of plural glass and plastic transparent covers also has a weight increasing factor.
A solar air heating system utilizing an absorber of highly polished sheet aluminum fins arranged in parallel is described by V. D. Bevill and H. Brandt, Solar Energy, Vol. 12 pp. 19-29 1968. According to Bevill et al the fins are disposed vertically - that is they were supported on their long edge being set in grooves in an aluminum base plate forming the bottom of a box horizontally positioned and having a horizontal glass cover. The solar radiation studied was at an angle of incidence less than 35.degree., the fins being in a fixed position. The solar radiation was reflected between adjacent highly polished fins and air was circulated between the fins. This system has proven highly desirable in many respects but has the unfortunate disadvantage of requiring an opaque cover or other shading mechanism particularly during the summer months in order to avoid unwanted and undesired heating to occur within the heater. Further, its efficiency was very sensitive to wind velocity, heat losses to ambient air being severe.
Accordingly, it is an object of this invention to obviate many of the disadvantages of the prior art solar heating apparatus.
Still another object of this invention is to obviate many of the disadvantages of prior art solar gas heating methods.
An additional object of this invention is to provide an improved solar gas heater utilizing generally horizontally disposed slats.
A still further object of this invention is to provide an improved method of absorbing and utilizing solar radiant energy using parallelly disposed heating slats.